In the design of aeroplanes, I have been constantly hampered by lack of reliable formulaæ that would give the thrust and horse-power required for a given diameter, pitch, speed, etc., of screws. The theoretical formulæ are too complex and uncertain for concrete computations, so I have undertaken an experimental study of air screws and have endeavoured to deduce formulæ, from the experimental data, which shall be reliable and at the same time cover the complexities that must enter with screws of widely differing elements such as blade area, form, pitch, etc.

M. S. Drzewiecki, in his excellent theoretical study of Air Screws, says “the question of screws in general is very complex, and poorly enough understood from a theoretical standpoint,” and we might add it is almost equally complex and little understood from the practical and experimental standpoint.